Guidewires for use in, for example, percutaneous transluminal coronary artery angioplasty (PTCA), must be thin and flexible enough to advance through small arteries within the coronary vasculature. These wires must also be sturdy enough to be manipulated from the outside of the body, such that a distal end of the wire can be brought into contact with a selected region of the coronary artery. Further, they must be strong enough to survive a "pull test" without breaking, to ensure that they do not come apart in the body.
Prior known guidewires each essentially include a solid tapered core and an elongated non-radiopaque coil or sleeve that is coincident with and extends over a distal portion of the core. The coil or sleeve adds strength to the tapered distal end of the core, essentially without limiting its flexibility. Each of the guidewires also has radiopaque material at its distal end. This allows the cardiologist to observe, using x-ray or fluoroscopy, the progress of the wire through the arteries. The remainder of the wire is non-radiopaque, to avoid obscuring the arteries from view.
One type of prior known guidewire includes a shorter radiopaque end coil that is attached to the distal end of the elongated non-radiopaque coil. The two coils have the same outer diameter and are typically made from coil wires that have the same thickness. The elongated coil is made from a material, such as stainless steel, which is relatively inexpensive. The shorter radiopaque coil is made from a precious metal, such as platinum, and is thus relatively expensive, even though it is fairly short.
A problem with this guidewire, beyond the expense of the radiopaque coil, is that it is difficult to assemble. The distal end of the elongated coil and the proximal end of the shorter coil must be held completely flush while they are welded or soldered together, to ensure a strong joint. Since these coils are each approximately 0.014 inch in diameter, it is difficult to hold them in proper alignment during the welding or soldering operation. There is also a danger that the two coils may become unattached during use. If this happens, the radiopaque coil may slide off the end of the essentially smooth core and become free in a patient's body.
Another type of known guidewire has small bands of radiopaque material wrapped around a non-radiopaque sleeve that covers the distal end of the wire. One of the problems with this guidewire is that the bands are so small that they are difficult to discern under x-ray or fluoroscopy. Accordingly, this guidewire may be difficult to use.
Another problem with the band-wrapped guidewire is that it is relatively expensive to manufacture. The assembly process necessarily includes the steps of wrapping the small bands around the wire and securing them to the wires such that the bands cannot be pulled off during use. The steps associated with attaching the bands to the guidewire are in addition to the conventional steps involved in guidewire manufacture.